Taskmgr Startup Errors - Windows Askmgr.exe" Specified In The Registry

A box came up with C:Windows askmgr.exe in the title bar and the text said, "Windows cannot access the specified device, path or file. You may not have the appropriate permissions to access them" I clicked OK and a second box came up. It had DESKTOP in the title bar and the text said "Could not load or run c: . Make sure the file exists on your computer or remove the reference to it in the registry." I clicked OK and things seemed to work.

I use the free version of Grisoft's AVG so I ran a scan and it found 3 items, one of which was taskmgr.exe infected with Trojan horse SHeur.NOZ. It said it fixed them so I rebooted. The other 2 were svchost.exe and svchost_tmp.exe also infected by SHeur.QCZ